The invention relates to electronic keyboards which make it possible to provide an interface for inputting information or instructions into an electronic machine (computer or the like) controlled by a user.
The keys of the keyboard are either keys each representing an alphanumeric character, or keys each providing for the execution of a specified function.
In certain cases, one desires the keys to be illuminated so as to be more visible. This mainly involves cases where the user needs to work in a nocturnal environment. For example, aeronautical standards demand that certain keys, or even all the keys, of certain keyboards be illuminated at night. Specifically, night flying of aircraft or helicopters is carried out from an unilluminated cockpit, and it is necessary for the functionally important keys to be perfectly visible and identifiable without error by the pilot.
The keyboard is generally composed of a printed circuit on which components are soldered, and among these components there are pressure-actuatable mini-switches. These switches are each situated under a respective key of the keyboard, and the pressure of the finger on the key is transmitted to the switch to actuate it.
The illumination of the key by backlighting from the rear is hampered by the presence of the switch component under the key. To provide this illumination, one generally uses light-emitting diodes soldered on the printed circuit alongside the switch, but the quantity of light emitted often proves to be insufficient to meet the requirements.
The invention proposes a different keyboard structure allowing the best possible illumination of the keys from the rear.
The subject of the invention is an electronic keyboard comprising a rigid printed circuit on which is soldered at least one switch which can be actuated indirectly by the finger of a user, an at least partly transparent key surmounting the switch and a means of illumination designed to illuminate the key from underneath the latter, light rays emanating from the means of illumination being visible to the user via the transparent part of the key, characterized in that the keyboard furthermore comprises a flexible printed circuit interposed between the key and the rigid printed circuit carrying the switch, in that the flexible printed circuit comprises a rigid part situated between the key and the switch, in that the means of illumination comprises a light-emitting diode soldered on the rigid part between the key and the switch and in that the key comprises a cavity surrounded by a peripheral edge, the diode being housed in the cavity and the peripheral edge coming to bear on the rigid part around the diode.
The flexible printed circuit comprises conductors for conveying current to the light-emitting diode.
Preferably, the transparent key has a hollow shape at the rear, with a peripheral edge surrounding a cavity, the diode being housed in the cavity; the peripheral edge comes to bear on the rigid part of the flexible printed circuit, around the diode. It is therefore via the periphery of the cavity that the key can apply a pressure to the rigid part of the flexible printed circuit. This pressure is transmitted to the switch by this rigid part.
The flexible printed circuit can be used as return spring for the key so as to restore the key to its rest position in the absence of any pressure exerted by the finger of the user.
The flexible printed circuit can be linked electrically directly to the rigid printed circuit, or else both of them may be linked separately to the electronic apparatus (computer or the like) controlled via the keyboard.